Sheet post-processing device, paper-made staple used in the device, and image forming device provided with the sheet post-processing device

ABSTRACT

A sheet post-processing device includes a stacker section that temporarily stores paper sheets as a paper sheet bundle, a stopper that regulates a carrying-in direction leading end of the paper sheet carried into the stacker section, a binding section that binds the paper sheet bundle regulated in position by the stopper, and folding rollers and a folding blade that perform folding processing for the sheet bundle bound by the binding section at a predetermined folding position of the paper sheet bundle. The binding section binds the paper sheet bundle with a paper-made staple. The stopper sets a position of the paper sheet bundle such that a binding position of the paper-made staple straddles the predetermined folding position. With this configuration, there can be provided a sheet-post processing device capable of folding the staple together with the paper sheet bundle.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a sheet post-processing device thatbinds paper sheets carried out from an image forming device such as aprinter or a copier and folds the bound paper sheets along apredetermined folding line and, more particularly, to a device capableof post-processing successively-carried out paper sheets.

2. Description of the Related Art

A sheet post-processing device that aligns paper sheets carried out froman image forming device and staples the paper sheets or folds the papersheets in a booklet form is widely known. Such a sheet post-processingdevice is provided with a plurality of sheet accumulation means forsheet post-processing. For example, in a processing tray as a firstsheet accumulation means, the paper sheets are accumulated in a bundleand are then stapled and, in a stacker section as a second sheetaccumulation means, the paper sheets accumulated in a bundle aresubjected to saddle stitching and then folded in a booklet form. Inrecent years, a binding processor that binds a paper sheet bundlewithout use of a metallic binding needle (metallic staple) in the sheetbundle binding processing and a sheet post-processing device are beingprovided.

For example, Jpn. Pat. Appln. Laid-Open Publication No. 2011-201698discloses a device that performs bookbinding without use of a metallicbinding staple so as to enhance recyclability and safety of the boundrecording material bundle. In this device, a folding blade and a foldingroller apply folding to a paper sheet bundle stacked on a stacker forstacking a plurality of paper sheets in order. A binding mechanismsection binds the paper sheet bundle, without use of the metallicstaple, in a position at a predetermined interval from a foldingposition where the paper sheet bundle is subjected to folding by thefolding blade and the folding roller.

In the binding processing, the binding mechanism section causesdeformation in a thickness direction of the paper sheet bundle that hasbeen subjected to folding by the folding blade and the folding roller soas to bind the paper sheet bundle. More specifically, upper and lowerconcavo-convex teeth crimping teeth are meshed with each other to causelocal deformation in the thickness direction of the paper sheet bundleto make the paper sheets to be engaged with each other.

Besides, there is known a cutter mechanism as a different type ofbinding mechanism from the binding mechanism using the crimping teeth.The cutter mechanism makes a cut in the paper sheet bundle fordeformation of the cut part so as to bind the paper sheet bundle. Morespecifically, the cutter mechanism binds the paper sheet bundle by meansof a U-shaped blade for making a U-shaped cut in the paper sheet bundle,a slit blade for forming a slit-like cut of a length corresponding to awidth of the U-shaped blade, and a pushing-in means for pushing theU-shaped cut formed by the U-shaped blade in the slit-like cut.

In either of the above two mechanisms, a portion to which the bindingmechanism applies binding is set so as to be separated by apredetermined interval from the folding position of the paper sheetbundle (refer to FIGS. 7 and 11 of Jpn. Pat. Appln. Laid-OpenPublication No. 2011-201698). In other words, the folding position andbinding position are shifted from each other.

Jpn. Pat. Appln. Laid-Open Publication No. 2013-126904 discloses adevice including a cut forming section that forms a cut bent in a convexshape on one side of a paper sheet bundle and a binding portion formingsection that forms, inside a range surrounded by the convex-shaped cut,a binding portion for binding the paper sheet bundle, wherein a lineconnecting both end portions of the convex-shaped cut is set as afolding line along which the paper sheet bundle is folded in two.

To be more specific, the above configuration is realized by a pressdevice. The press device is provided with a punch section and a diesection and configured to apply punching to the paper sheet bundle bythe punch section. The punch section has an engagement piece formingblade, a hole forming blade, and a cut forming blade (FIG. 5). Theengagement piece forming blade makes a cut in the paper sheet blade toform an engagement piece in the paper sheet. The hole forming bladeforms, in the paper sheet, a locking piece which is a hole through whichthe engagement piece is inserted. The cut forming blade forms a cut inthe paper sheet. The cut forming blade is bent (curved) into a shapeprotruding to one side. Both end portions of the engagement pieceforming blade and both end portions of the cut forming blade arepositioned on the same straight line. The paper sheet bundle is conveyedsuch that the folding line of the sheet bundle coincides with thestraight line. On the other hand, the die section has a first insertionhole into which the engagement piece forming blade is inserted, a secondinsertion hole into which the hole forming blade is inserted, and athird insertion hole into which the cut forming blade is inserted.

Thus, the both end portions of the engagement piece forming blade andboth end portions of the cut forming blade are positioned on the samestraight line, and the folding line is set on this straight line. Thatis, as in Jpn. Pat. Appln. Laid-Open Publication No. 2011-201698, thefolding position and binding position are shifted from each other.

Japanese Patent No. 4,952,129 discloses a stapler device that uses apaper-made staple in place of a metallic staple in consideration ofenvironment and safety. In this device, an operator manually inserts apaper sheet bundle into a binding processing port. More specifically,Japanese Patent No. 4,952,129 discloses a desk-top type stapler device.In this device, a paper-made staple at the top of a connected staple inwhich a plurality of substantially straight shaped paper-made staple areconnected in parallel is cut off from the connected staple and shapedinto a substantially U-form. Then, both leg portions of the paper-madestaple are made to penetrate paper sheets to be bound, bent along thepaper sheets to be bound, and then bonded to each other. With thisconfiguration, it is possible to bind the paper sheets to be bound withan easily deformable paper-made staple.

All of the above disclosed inventions are devices that bind the papersheet bundle at a middle portion thereof and have a configuration inwhich the folding position and binding position are shifted from eachother. The invention disclosed in Japanese Patent No. 4,952,129 is adevice that does not use a metallic staple but uses a paper-made stapleto bind the paper sheet bundle.

When the binding processing and folding processing are performed withoutuse of the metallic staple in the above sheet post-processing devicesthat align paper sheets carried out from an image forming device or thelike and staples the paper sheets or folds the paper sheets in a bookletform, the following problems arise in terms of device configuration.

As disclosed in Jpn. Pat. Appln. Laid-Open Publications No. 2011-201698and No. 2013-126904, a portion to which the binding mechanism appliesbinding is set so as to be separated by a predetermined interval fromthe folding position of the paper sheet bundle. In other words, abooklet is formed with the folding position and binding position shiftedfrom each other. However, as compared with a configuration in which astapler position (binding position) and folding position are set atsubstantially the same position, a page opening range differs between apage where the binding position is formed and a page where the bindingposition is not formed due to shifting of the binding position from thefolding position.

Thus, unless a printing area is reduced for the page having the bindingposition, image missing may occur. Further, when the folding position isset at a half position of a length of the paper sheet, since the bindingposition is shifted from the folding position, the first half pages canbe turned beyond the folding position, whereas the remaining half pagescan be turned only to the binding position separated away from thefolding position. Thus, unbalance is generated in the page opening rangein the same booklet, causing a feeling of strangeness.

The binding mechanisms disclosed in Jpn. Pat. Appln. Laid-OpenPublications No. 2011-201698 and No. 2013-126904 are each configured tobind the paper sheet bundle by deforming the paper sheets themselves.For example, upper and lower concavo-convex teeth crimping teeth aremeshed with each other to cause the deformation in the thicknessdirection of the paper sheet bundle to make the paper sheets to beengaged with each other. However, it is necessary to mesh the upper andlower concavo-convex crimping teeth with a considerable crimping forcein order to make the paper sheets to be engaged with each other. Aninsufficient crimping force results in insufficient binding, that is,only the crimping force cannot make the binding state staple. When thebinding position is made to coincide with the folding position in thebinding mechanism using this crimping mechanism, a deformation force dueto curve of the paper sheets acts to affect binding performance.

Further, as another binding mechanism, there is known the mechanismincluding a cut forming section that forms a cut bent in a convex shapeon one side of a paper sheet bundle and a binding portion formingsection that forms, inside a range surrounded by the convex-shaped cut,a binding portion for binding the paper sheet bundle, wherein theconvex-shaped cut is inserted into the binding portion for binding. Inthis case, a comparatively large cut is formed in the paper sheetsthemselves, so that damage is given to the paper sheets themselves, andouter appearance is affected.

Under such circumstances, the binding mechanism by the paper-made stapleas disclosed in Japanese Patent No. 4,952,129 that binds the paper sheetbundle without use of the crimping mechanism or without forming largecut in the paper sheets can be considered effective. However, in thismechanism, the operator manually inserts an end edge of the paper sheetbundle into a binding processing port, and the configuration describedabove, in which the paper sheet bundle is folded at the half position ofthe paper sheet length and bound is not considered at all. As a matterof course, a configuration in which the binding position of the papersheet bundle and folding position are set at substantially the sameposition is not described.

Under such circumstances, the present inventor examines a configurationin which the paper-made staple is used to bind the paper sheet bundle atthe half position of the paper sheet length and seeks to provide a sheetpost-processing device capable of demonstrating a comparatively largebinding force, capable of allowing left and right pages to be openedevenly upon page turning, capable of using the paper-made staple in thesame way as the metallic one, and capable of providing an environmentalbenefit, and an image forming device adopting the sheet post-processingdevice.

SUMMARY OF THE INVENTION

To solve the above problem, according to a first aspect of the presentinvention, there is provided a sheet post-processing device that bindsand holds paper sheets, the device including: a stacker section thattemporarily stores the paper sheets as a paper sheet bundle; a movablestopper that regulates the sheet bundle carried into the stackersection; a binding section that binds the paper sheet bundle regulatedin position by the stopper; a folding section that folds the paper sheetbundle bound by the binding section at a predetermined folding positionof the paper sheet bundle; and a controller that controls movement ofthe stopper. The binding section binds the paper sheet bundle at apredetermined binding position with a paper-made staple. The controllercontrols the movement of the stopper such that the paper-made staple ispositioned so as to straddle the predetermined folding position.

According to a second aspect of the present invention, there is provideda sheet post-processing device that binds and holds paper sheets with apaper-made stapler. The paper-made staple is configured to bind a papersheet bundle, straddling a predetermined folding position of the papersheet bundle and to be folded by folding rollers and a folding blade ofthe sheet post-processing device together with the paper sheet bundle.The paper-made staple includes a pair of leg portions inserted into thepaper sheet bundle and then bent inward and a staple connection portionthat connects the leg portions in a staple longitudinal direction. Theconnection portion has a cut in a direction crossing a longitudinaldirection thereof at a position corresponding to the folding positionfor the purpose of facilitating the folding thereof, and each of the legportions has a leg portion side cut at a position overlapping the cut ofthe connection portion when the leg portions are bent inward.

According to the first aspect of the present invention, the foldingsection is configured to perform the folding processing for the papersheet bundle bound by the binding section at the folding position of thepaper sheet bundle, and the binding section is configured to bind thepaper sheet bundle with the paper-made staple and set a sheet positionsuch that the binding position of the paper-made staple straddles thefolding position. With the above configuration, the paper-made staplethat straddles the folding position is also folded simultaneously withthe folding of the paper sheet bundle, thereby increasing bindingstrength of the paper sheet bundle to be saddle stitched. Further, sincea large cur portion is not formed in the paper sheet bundle, the openingportion of the paper sheet bundle is small to give less damage to thepaper sheet. Further, since a metallic staple is not used, increasingboth environmental protection and safety.

According to the second aspect of the present invention, the paper-madestaple has a pair of leg portions inserted into the paper sheet bundleand then bent inward and a staple connection portion that connects theleg portions in a staple longitudinal direction. The connection portionhas a cut in a direction crossing a longitudinal direction thereof atthe edge portion thereof so as to correspond to the folding position forthe purpose of facilitating the folding thereof. Thus, when the foldingoperation is performed by the folding blade and folding rollers, thestaple itself is easily and reliably folded along the cut, facilitatingthe folding of the paper-made staple.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory view illustrating an entire configuration of animage forming system according to the present invention;

FIG. 2 is an explanatory view illustrating an entire configuration of asheet post-processing device according to the present invention providedwith a sheet folding unit;

FIG. 3 is an explanatory view illustrating a part of the sheet foldingunit of FIG. 2;

FIG. 4 is an explanatory view of the sheet folding unit;

FIG. 5 is an explanatory view illustrating a saddle stitching stapler(non-separated type) of the sheet post-processing device of FIG. 4;

FIG. 6 is a view illustrating a state where the saddle stitchingstaplers of FIG. 5 are mounted to a stacker;

FIG. 7 is an explanatory view illustrating a state where a paper sheetbundle is bound at a position straddling a folding position of the papersheet bundle by the saddle stitching stapler of FIG. 6;

FIGS. 8A to 8C are explanatory views each illustrating a mechanism thatbinds the paper sheet bundle using the saddle stitching stapler of FIG.5;

FIG. 9 is an explanatory view illustrating a saddle stitching stapler(separated type) of the sheet post-processing device of FIG. 4;

FIG. 10 is a view illustrating a state where the saddle stitchingstaplers of FIG. 9 are mounted to the stacker;

FIG. 11 is an explanatory view illustrating a state where the papersheet bundle is bound at a position straddling the folding position ofthe paper sheet bundle by the saddle stitching stapler of FIG. 9;

FIGS. 12A to 12C are explanatory views each illustrating the paper-madestaple loaded into the saddle stitching stapler of the presentinvention, in which FIG. 12A is an explanatory view illustrating a statewhere a plurality of the paper-made staples are connected, FIG. 12B is aperspective view of the paper-made staple, and FIG. 12C is across-sectional view illustrating a state where the paper sheet bundleis bound with the paper-made staple;

FIG. 13 is an explanatory view illustrating a state where a number ofpaper-made staples are wound in a roll shape;

FIGS. 14A and 14B illustrate another embodiment of the paper-made stapleto be applied to the sheet to be bound, in which FIG. 14A is anexplanatory view illustrating a connected state of the paper-madestaples, and FIG. 14B is a cross-sectional view illustrating a statewhere the paper sheet bundle is bound with the paper-made staple;

FIGS. 15A to 15D are explanatory views of operation of the sheet bundlefolding unit illustrated in FIGS. 2 and 4, in which FIG. 15A is a viewillustrating a state where the paper sheet bundle bound with thepaper-made staple is set at the folding position, FIG. 15B is an initialstate view of operation of folding the paper sheet bundle and paper-madestaple from a leg portion side, FIG. 15C is a view illustrating a statewhere the paper sheet bundle and paper-made staple are inserted into anip position between folding rollers, and FIG. 15D is a carry-out stateview where the paper sheet bundle and paper-made staple are folded bythe folding rollers;

FIG. 16 is a perspective view illustrating a state where the paper sheetbundle and paper-made staple are folded;

FIG. 17 is a view explaining positions and shapes of the folding rollerand folding blade of the sheet bundle folding unit of FIGS. 2 and 4 andpaper-made staple;

FIG. 18 is a view explaining positions and shapes of the folding rollerand folding blade of a sheet bundle folding unit according to anotherembodiment and a paper-made staple;

FIGS. 19A and 19B are explanatory views each illustrating a positionalrelationship between the paper-made staple and folding blade, in whichFIG. 19A is a view illustrating a state where the leg portions of thepaper-made staple overlap each other at an abutting position of thefolding blade, and FIG. 19B is a view illustrating a state where the legportions of the paper-made staple do not overlap each other at theabutting position of the folding blade; and

FIG. 20 is an explanatory view of a control configuration of the systemof FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the present invention will be described based on apreferred embodiment illustrated. FIG. 1 is an explanatory viewillustrating an entire configuration of an image forming systemaccording to the present invention, FIG. 2 is an explanatory viewillustrating an entire configuration of a sheet post-processing device,and FIG. 3 is an explanatory view illustrating a detailed configurationof a sheet folding unit. The image forming system illustrated in FIG. 1includes an image forming device A and a sheet post-processing device B,and the sheet post-processing device B incorporates a sheet saddlestitching device C.

[Configuration of Image Forming Device]

The image forming device A illustrated in FIG. 1 feeds a paper sheetfrom a sheet supply section 1, performs printing in an image formingsection 2, and discharges the paper sheet after printing from a mainbody discharge port 3. Paper sheets of a plurality of sizes areaccommodated in sheet cassettes 1 a and 1 b, and the sheet supplysection separates, one from the other, paper sheets of a specified sizeand feeds them one by one to the image forming section 2. The imageforming section 2 includes an electrostatic drum 4 and a print head(laser emitter) 5, a developing unit 6, a transfer charger 7, and afixing unit 8 which are disposed around the electrostatic drum 4. Anelectrostatic latent image is formed on the electrostatic drum 4 usingthe laser emitter 5, the developing unit 6 adds toner to the image, thetransfer charger 7 transfers the image onto the paper sheet, and thefixing unit 8 thermally-fixes the image. The paper sheet with thusformed image is sequentially carried out from the main body dischargeport 3. A reference numeral 9 in FIG. 1 denotes a circulation path,which is a path for two-side printing in which the paper sheet printedon the front side from the fixing unit 8 is reversed via a main bodyswitchback path and is fed to the image forming section 2 again forprinting on the back side of the paper sheet. The paper sheet thusprinted on both sides is reversed in the main body switchback path 10and is carried out from the main body discharge port 3.

A reference numeral 11 in FIG. 1 denotes an image reader, where adocument sheet set on a platen 12 is scanned by a scan unit 13 and iselectrically read by a photoelectric conversion element 14 through areflective mirror and a condensing lens. This image data is subjectedto, e.g., digital processing by an image processor and is subsequentlytransferred to a data storage section 17, and an image signal is sent tothe laser emitter 5. A reference numeral 15 denotes a document feederthat feeds document sheets stored in a stacker 16 to the platen 12.

The image forming device A having the above-described configuration isprovided with a control section (controller). Image forming conditionsare set via a controller panel 18, for example, printout conditions suchas a sheet size specification, a color or black-and-white printingspecification, a print copy count specification, single- or double-sideprinting specification, and enlarged or reduced printing specification.On the other hand, in the image forming device A, image data read by thescan unit 13 or transferred through an external network is stored in thedata storage section 17. The image data stored in the data storagesection 17 is transferred to a buffer memory 19, which sequentiallytransfers data signals to the laser emitter 5.

Simultaneously with the image forming conditions, post-processingconditions are input and specified via the controller panel 18. Forexample, a “printout mode”, a “stapling mode”, and a “sheet bundlefolding mode” are specified as the post-processing conditions. The imageforming device A forms an image on the paper sheet in accordance withthe image forming conditions and the post-processing conditions.

[Configuration of Sheet Post-Processing Device]

The sheet post-processing device B connected to the above-describedimage forming device A receives a paper sheet with the image formedthereon from the main body discharge port 3 of the image forming deviceA and is configured to (1) store the paper sheet in a first sheetdischarge tray 21 (“printout mode” as described above), (2) align thepaper sheets from the main body discharge port 3 in a bundle to staplethem and then store the paper sheets in the first sheet discharge tray21 (“stapling mode” as described above), or (3) align the paper sheetsfrom the main body discharge port 3 in a bundle, then fold the papersheets in a booklet form, and store the paper sheets in a seconddischarge tray 22 (“sheet bundle folding mode” as described above).

Thus, as illustrated in FIG. 2, the sheet post-processing device B isprovided with the first sheet discharge tray 21 and second sheetdischarge tray 22 in a casing 20. Further, the device B is provided witha sheet carry-in path P1 having a carry-in port 23 continued to the mainbody discharge port 3. The sheet carry-in path P1 is formed of astraight-line path in a substantially horizontal direction in the casing20. Further, there are provided a first switchback conveying path SP1and a second switchback conveying path SP2 that branch off from thesheet carry-in path P1 to transport a paper sheet in an inversedirection. The first switchback conveying path SP1 branches off from thesheet carry-in path P1 to the downstream side of the sheet carry-in pathP1, the second switchback conveying path SP2 branches off from the sheetcarry-in path P1 to the upstream side of the sheet carry-in path P1, andthe paths SP1 and SP2 are disposed spaced apart from each other.

In such a path configuration, in the sheet carry-in path P1, there aredisposed a carry-in roller 24 and sheet discharge roller 25, and therollers are coupled to a drive motor M1 (see FIG. 20) capable ofrotating forward and backward. Further, in the sheet carry-in path P1,there is disposed a path switching piece 27 for guiding a paper sheet tothe second switchback conveying path SP2, and the piece 27 is coupled toan operation means such as a solenoid. Further, the sheet carry-in pathP1 has, on the downstream side of the carry-in roller 24, a punch device28 for punching the paper sheet from the carry-in port 23. Theillustrated punch device 28 is configured to be detachably mounted tothe casing 20 depending on a device specification.

[Configuration of First Switchback Conveying Path SP1]

The first switchback conveying path SP1 disposed, as illustrated indetail in FIGS. 2 and 3, on the downstream side (rear end portion of thedevice) of the sheet carry-in path P1 is configured as described below.The sheet carry-in path P1 is provided, at its exit end, with the sheetdischarge roller 25 and a sheet discharge port 25 a. A level differenceis formed from the sheet discharge port 25 a, and a processing tray 29constituting a first processing tray is provided on the downstream side.The processing tray 29 includes a tray for loading and supporting thepaper sheet discharged from the sheet discharge port 25 a. There isdisposed, above the processing tray 29, a forward/backward rotationroller 30 capable of moving up and down between a position to come intocontact with the paper sheet on the tray and a standby position(chain-line position in FIG. 3) spaced apart from the contact position.The forward/backward rotation roller is coupled with a forward/backwardrotation motor M2 (see FIG. 20) and is controlled to rotate in aclockwise direction in FIG. 3 when a paper sheet approaches theprocessing tray 29, while rotating in a counterclockwise direction aftera paper sheet rear end enters the tray. Thus, the first switchbackconveying path SP1 is configured above the processing tray 29. Areference numeral 31 in FIG. 3 denotes a caterpillar belt, and its onepulley side is brought into press-contact with the sheet dischargeroller 25. The caterpillar belt 31 is axially supported so as to bepivotable about a shaft on the one pulley side so that a leading endpulley side droops onto the processing tray 29. A reference numeral 30 bin FIG. 3 denotes a driven roller engaged with the forward/backwardrotation roller 30. The driven roller 30 b is provided in the processingtray 29.

Further, the first sheet discharge tray 21 is located downstream of thefirst switchback conveying path SP1 and is configured to support aleading end of paper sheet guided to the first switchback conveying pathSP1 and second switchback conveying path SP2.

With the above-described configuration, the paper sheet from the sheetdischarge port 25 a reaches the processing tray 29 and is transferredtoward the first sheet discharge tray 21 by the forward/backwardrotation roller 30. Once the rear end of the paper sheet reaches theprocessing tray 29, the forward/backward rotation roller 30 is reverselyrotated (counterclockwise in the figure) to transfer the paper sheet onthe processing tray 29 in a direction opposite to a sheet dischargedirection. At this time, the caterpillar belt 31 cooperates with theforward/backward rotation roller 30 to switchback-convey the rear end ofthe paper sheet along the processing tray 29.

A rear end regulating member 32 and an end surface stapler 33 aredisposed at a rear end portion of the processing tray 29 in the sheetdischarge direction. The rear end regulating member 32 regulates aposition of the rear end of the paper sheet. The illustrated end surfacestapler 33 staples a paper sheet bundle collected on the tray at one ormore positions. The rear end regulating member 32 is also used toprovide a function of carrying out the stapled paper sheet bundle to thefirst sheet discharge tray 21, located downstream of the processing tray29. To this end, the rear end regulating member 32 is configured to beable to reciprocate in the sheet discharge direction along theprocessing tray 29. A carry-out mechanism of the illustrated rear endregulating member 32 has a grip pawl that grips the paper sheet bundleand a rear end regulating surface 32 b against which the sheet rear endabuts for regulation. The rear end regulating member 32 is configured tobe movable in the left-right direction in the figure along a guide railprovided on a device frame. A reference numeral 34 a denotes a drivingarm that reciprocates the rear end regulating member 32. The driving arm34 is coupled to a sheet discharge motor M3 (see FIG. 20).

The processing tray 29 has a side aligning plate 34 b with which thepaper sheets collected on the tray are aligned in a width directionthereof. The side aligning plate 34 b includes a pair of left and right(front and rear in FIG. 3) aligning plates so as to align the papersheets with reference to a sheet center and is configured to approachand leave the sheet center. The side aligning plate 34 b is coupled to anot illustrated aligning motor.

The first switchback conveying path SP1 configured as described abovealigns the paper sheets from the sheet discharge port 25 a on theprocessing tray 29 in the “stapling mode” as described above, and theend surface stapler 33 staples the paper sheet bundle at one or moreportions of the rear end edge of this paper sheet bundle. In the“printout mode”, a sheet from the sheet discharge port 25 a is notsubjected to the switchback, but the sheet conveyed along the processingtray 29 is made to pass between the forward/backward rotation roller 30and driven roller 30 b and carried out to the first sheet discharge tray21. Thus, the illustrated device is characterized in that the sheet tobe stapled is bridged between the processing tray 29 and the first sheetdischarge tray 21 to allow the device to be compactly configured.

[Configuration of Second Switchback Conveying Path SP2]

The following describes a configuration of the second switchbackconveying path SP2 branching off from the sheet carry-in path 21. Asillustrated in FIG. 4, the second switchback conveying path SP2 islocated in a substantially vertical direction inside the casing 20. Aconveying roller 36 is located at an inlet of the second switchbackconveying path SP2, and a conveying roller 37 is located at an outlet ofthe second switchback conveying path SP2. A stacker section 35constituting a second processing tray that aligns and temporarilycollects the paper sheets fed along the second switchback conveying pathSP2 is provided downstream of the second switchback conveying path SP2.The illustrated stacker section 35 includes a conveying guide thattransfers the paper sheets. A saddle stitching stapler 40 and foldingroller 45 are arranged along the stacker section 35. The configurationof these components will be sequentially described below.

The conveying roller 36, located at the inlet of the second switchbackconveying path SP2, is configured to be rotatable forward and backward.A sheet carried into the first switchback conveying path SP1 locateddownstream is temporarily held (temporarily reside) on the secondswitchback conveying path SP2. The reason for the temporary holding isas follows. That is, the preceding paper sheets are stapled by the endsurface stapler 33, and the resultant sheet bundle is carried out to thefirst sheet discharge tray 21. During this carry-out, a paper sheet fedfrom the image forming device A to the sheet carry-in path P1 istemporarily held on the second switchback conveying path SP2. Then,after the processing of the preceding paper sheet bundle is finished,the standing-by sheet is conveyed from the first switchback conveyingpath SP1 onto the processing tray 29.

The stacker section 35 is formed of a guide member that guides the papersheet being conveyed. The stacker section 35 is configured so that thepaper sheets are loaded and housed thereon. The illustrated stackersection 35 is connected to the second switchback conveying path SP2 andlocated in a center portion of the casing 20 so as to extend in thesubstantially vertical direction. This allows the device to be compactlyconfigured. The stacker section 35 is shaped to have an appropriate sizeto house maximum sized paper sheets. In particular, the illustratedstacker section 35 is curved or bent so as to project toward the area inwhich the saddle stitching stapler 40 and folding roller 45 to bedescribed later are arranged.

A switchback approaching path 35 a is connected to a conveying directionrear end of the stacker section 35. The switchback approaching path 35 aoverlaps the outlet end of the second switchback conveying path SP2.This is to allow the rear end of a carried-in (succeeding) paper sheetfed from the conveying roller 37 on the second switchback conveying pathSP2 to overlap the rear end of the loaded (preceding) paper sheetssupported on the stacker section 35 to ensure the page order of thecollected paper sheets. A leading end regulating member (hereinafter,referred to as stopper 38) regulating a sheet leading end in theconveying direction is located downstream of the stacker section 35. Thestopper 38 is supported by a guide rail and the like so as to be movablealong the stacker section 35. The stopper 38 is moved between positionsSh1 and Sh2 and Sh3, illustrated in the figure, by a shift means controlcircuit MS (see FIG. 20). This point will be described later inconnection with a controller of the stopper 38.

[Configuration of Saddle Stitching Stapler]

The following describes the saddle stitching stapler 40 with referenceto FIGS. 5 to 11. As illustrated in FIG. 4, a binding position X and afolding position Y are set at the upstream side and downstream side,respectively, along the above-described stacker section 35. The saddlestitching stapler 40 that binds the sheet bundle with a paper-madestaple 60 is disposed at the binding position X. The saddle stitchingstapler 40 includes a driver unit 41 and a clincher unit 42 which arearranged opposite to each other across the stacker section 35. Thedriver unit 41 drives a paper-made staple 60 into a paper sheet bundle100. The clincher unit 42 bends leg portions 61 and 62 of the drivenpaper-made staple 60 in a direction facing each other and bonds the legportions 61 and 62 to each other. The driver unit 41 and clincher unit42 face each other across the stacker section 35.

The saddle stitching stapler 40 illustrated in FIGS. 5 to 8 is of anon-separated type in which the driver unit 41 and clincher unit 42 areintegrally formed with a frame 108 and not separated from each other,while the saddle stitching stapler 40 illustrated in FIGS. 9 to 11 is ofa separated type in which the driver unit 41 and clincher unit 42 areseparated up and down.

FIGS. 12 to 14, to be described later, illustrate a configuration of thepaper-made staple 60 loaded into the saddle stitching stapler 40 andbinds the paper sheet bundle. The paper-made staple 60 referred to inthe present application is a paper-made staple needle for binding thepaper sheet bundle. The paper-made staple need not be fully made ofpaper, but a material of the paper-made staple may be a thin plasticmaterial or the like as long as it has flexibility equivalent to thepaper and environmental protection property (e.g., capable of beingdiscarded without being classified from papers).

First, an overview of the saddle stitching stapler of a non-separatedtype illustrated in FIGS. 5 to 8 will be described. As illustrated inFIG. 5, the saddle stitching stapler 40 includes a frame 108 and a base109. The frame 108 has a sheet insertion port 107 positioned below adrive motor 56 that performs staple drive when the saddle stitchingstapler 40 performs binding operation with the paper-made staple 60,through which paper sheets to be bound are inserted. The base 109supports the drive motor 56 and frame 108.

As illustrated in FIG. 5, the drive motor 56 is rotatably mounted to anupper portion of the frame 108. The drive motor 56 rotates a driver cam52 when performing the binding operation. When a rolled staple 70 inwhich a number of paper-made staples 60 are connected is loaded into astaple holder 111 (to be described later) of the frame 108, a staplecover 106 positioned to the left of the drive motor 56 is released toopen an upper surface of the frame 108.

The frame 108 has, at its rear end portion, a staple cartridge 51 as astaple loading section for loading the rolled staple 70. The frame 108further has a substantially planar conveying path 113 as a stapleconveying path for conveying the paper-made staple 60 frontward from thestaple holder 111. Although not illustrated, a plate spring is providedon both left and right sides of the conveying path 113.

The frame 108 has, near a front end portion of the conveying path 113,the drive motor 56 that rotates the driver cam 52. Further, the frame108 has, below the driver cam 52, a forming plate 115 as a staplecutting/shaping section for cutting the paper-made staple and shaping itinto a substantially U-shape. The forming plate 115 performs cutting andshaping of the paper-made staple 60. The frame 108 further has a driverunit 41 as a staple penetrating section for making the paper-made staple60 penetrate the paper sheets to be bound by the drive of the drivemotor 56. The driver unit 41 has a driver 53 that moves up and down acutter blade 71 for forming a hole penetrating the paper sheets. Theframe 108 further has a sheet presser 119 for pressing the paper sheetto be bundled upon cutting, shaping, and penetration.

The frame 108 further has, below the conveying path 113, a pusher 117biased frontward by a spring, as a moving mechanism for moving thepaper-made staple 60 from a position at which the above-describedcutting and shaping of the paper-made staple 60 is performed to aposition at which the penetration of the paper-made staple 60 into thepaper sheet bundle 100 is performed. There is provided, below theforming plate 115, driver 53, sheet presser 119, and pusher 117, a sheetinsertion port 107 through which the sheet bundle to be bound and atable 120 on which the sheet bundle to be bound is placed.

There is provided, below the table 120, a bending section that bends,along the paper sheet bundle 100, the leg portions 61 and 62 of thedriven paper-made staple 60 that has penetrated the paper sheet bundle100 at the penetration position and bonds the leg portions 61 and 62 toeach other. The saddle stitching stapler 40 has, as the bending section,the clincher unit 42, a pushing unit 124, and a clincher slider 123 anduses a clincher motor 122 to move the pushing unit 124 and clincherslider 123 at an appropriate timing. In the saddle stitching stapler 40,there is provided, on a clincher base 130, the clincher unit 42 servingas the bending section and including a clincher lifter 129 that supportsand positions a clincher center 127 and a clincher left 128.

The saddle stitching stapler 40 has the configuration as describedabove. That is, the driver unit 41 is moved based on operation of thedrive motor 56 with respect to the paper sheet bundle 100 placed on thetable 120 inserted through the sheet insertion port 107. Then, holes areformed so as to penetrate the paper sheet bundle 100, and the paper-madestaple 60 is inserted through the holes to bind the paper sheet bundle100.

FIGS. 8A to 8C are views each illustrating the cutter blade 71 providedat a leading end of the driver 53 illustrated in FIG. 5 and configuredto allow the paper-made staple 60 to penetrate the paper sheet bundle100 and its operation. FIG. 8A illustrates a state where the paper-madestaple 60 formed into the U-shape by the forming plate 115 is set to thecutter blade 71 by the pusher 117. When the driver unit 41 moves down ina state where the paper-made staple 60 is set to the cutter blade 71,the cutter blade 71 is inserted into the paper sheet bundle 100 whileretaining the paper-made staple 60, as illustrated in FIG. 8B.Thereafter, the leg portions 61 and 62 of the paper-made staple 60 arebent inward by the pushing unit 124 and clincher unit 42 and bonded toeach other. Synchronously with this operation, the driver 53 movesupward, and the paper sheet bundle 100 is bound by the paper-made staple60. The cutter blade 71 returns to its original position as illustratedin FIG. 8C and waits for next paper-made staple 60. In this manner, thepaper sheet bundle 100 is bound.

Configurations of respective parts of the saddle stitching stapler 40are described in detail in Japanese Patent No. 4,952,129 quoted above,so descriptions thereof are omitted here.

The following describes arrangement of the stacker section 35 of thesaddle stitching stapler 40 using FIG. 6. FIG. 6 illustrates a statewhere the saddle stitching stapler 40 illustrated in FIG. 5 is disposedat left and right positions that cross a sheet conveying direction. Thatis, left and right carriages 43 having thereon the left and right saddlestitching staplers 40, respectively, are placed on the stacker section35 so as to be movable in accordance with a length of the paper sheet inthe width direction. In both the left and right saddle stitchingstaplers 40, the forming plate 115 that forms the paper-made staple 60into a crown shape and the drive motor 56 that moves the driver 53 thatdrives the paper-made staple 60 into the paper sheet bundle areconnected to the driver cam 52 through a transmission belt 55. Thus, thedriver cam 52 is rotated by the drive of the drive motor 56 to drive thepaper-made staple 60 into the paper sheet bundle 100. At the same time,both the leg portions 61 and 62 are bent inward by the clincher unit 42and then bonded to each other at an adhesive portion 63 thereof, whichis coated with an adhesive. The paper-made staple 60 is housed in thestaple cartridge 51 of the saddle stitching stapler 40 and is cut into asize to be driven by the stapler.

The paper sheets to be saddle-stitched are conveyed to the saddlestitching stapler 40 thus configured, and leading ends thereof in theconveying direction are made to abut against the stopper 38, asillustrated in FIGS. 2 and 3 to be sequentially stacked in the stackersection 35. In this stacking, as described above, when the stopper 38 ispositioned at the position Sh3 in FIG. 4, a rear end of the paper sheet(bundle) supported by the stacker section 35 enters the switchbackapproaching path 35 a, so that a subsequent paper sheet fed from thesecond switchback conveying path SP2 in this state is reliably stackedon the stacked paper sheets. Thereafter, in accordance with thecarrying-in of the subsequent paper sheets, the stopper 38 is moved tothe position Sh1 side for stacking thereof in the stacker section 35.When the stopper 38 is positioned at the position Sh2 in FIG. 4, acenter of the paper sheet (bundle) supported in the stacker section 35is positioned to a binding position X (to be described later) of thesaddle stitching stapler 40. When the stopper 38 is positioned at theposition Sh1 in FIG. 4, the center of the paper sheet bundle 100 stapledand supported by the stacker section 35 is positioned to a foldingposition Y which is a position at which a folding blade 46 is insertedbetween folding rollers 45. Thus, the positions Sh1, Sh2, and Sh3correspond respectively to a folding position, a binding position, and asubsequent sheet receiving position. This point will be described later.

For example, when the center portion of the elevated paper sheet bundle100 in the conveying direction (length direction) coincides with thebinding position X in FIGS. 4 and 6, movement of the paper sheet bundle100 is stopped by the stopper 38, and drive of the paper-made staple 60is waited for. The binding position X of the paper sheet and foldingposition Y are set to the same position, that is, the binding positionalso serves as the folding position.

FIG. 7 illustrates a state where the paper-made staple 60 is driven intothe paper sheet bundle 100 by the saddle stitching stapler 40 tocomplete the binding processing of the paper sheet bundle 100. Theposition of the paper sheet bundle 100 is set by the movement of thestopper 38 such that the paper-made staple 60 straddles the foldingposition in the sheet conveying direction. In FIG. 7, the leg portions61 and 62 of the left and right paper-made staples 60 are driven,sandwiching the folding position Y therebetween such that a center of aconnection portion (hereinafter, referred to as “staple leg portionconnection portion 60 a”) of the leg portions 61 and 62 substantiallycoincides with the folding position Y. With this configuration, thestaple leg portion connection portion 60 a of the paper-made staple 60is easily folded with the leg portions 61 and 62 inside upon folding ofthe paper sheet bundle. That is, the paper-made staple 60 is positionedin a substantial center portion of the paper sheet bundle 100 in theconveying direction, straddling the folding position, so as to bind thepaper sheet bundle 100.

[Another Embodiment of Saddle Stitching Stapler/Vertically SeparatedType]

Thus far, the saddle stitching stapler 40 of a non-separated type inwhich the driver 53 side and clincher unit 42 side are not separatedfrom each other has been described. This saddle stitching stapler 40 hasa configuration that an extending direction of the staple leg portionconnection portion 60 a of the paper-made staple 60 is set to the samedirection as the sheet conveying direction and that the binding positionis set so as to straddle the sheet folding position and can thus beconfigured as the non-separated type. On the other hand, with aseparated type, as illustrated in FIGS. 9 to 11, in which the driver 53side and clincher unit 42 side are separated from each other, it ispossible to set the binding position at a position near the center ofthe paper sheet bundle in the width direction.

The following describes this separated type. The same reference numeralsare given to the same functions as those of the non-separated type, anddetailed descriptions thereof are omitted. As illustrated in FIG. 9, thedriver unit 41 side and clincher unit 42 side are completely separatedup and down. Thus, the mechanism, such as the driver 53, constitutingthe driver unit 41 is placed on a base 109 serving also as an uppersheet guide. On the other hand, a mechanism part of the clincher unit 42is placed on a clincher base 130. Accordingly, the paper sheet bundle100 to be bound is conveyed from a near side of FIG. 9 to a far sidethereof along the table 120.

In FIG. 10, the saddle stitching staplers 40 illustrated in FIG. 9 eachhaving a configuration in which the driver 53 side and clincher unit 42side are completely separated up and down are mounted side by side alongthe binding position X. In this case, the entire bodies of the saddlestitching staplers 40 can be disposed within the stacker section 35, awidth direction size can be made more compact than that illustrated inFIG. 6. Since other mechanisms are the same as those of the saddlestitching stapler 40 of FIG. 6, the descriptions thereof are omitted.

In this saddle stitching stapler 40, the driver unit 41 and clincherunit 42 are separated and face each other so as to allow the paper sheetbundle 100 to pass therebetween. This allows the paper sheet bundle 100to be staple-bound at its center portion or other arbitrary position.

The paper sheets to be saddle-stitched are conveyed to the saddlestitching stapler 40 thus configured, and leading ends thereof in theconveying direction are made to abut against the stopper 38 serving asthe leading end regulating member to be sequentially stacked in thestacker section 35. The stacking position is, as described above, set bythe stopper 38 moving from the positions Sh1 to Sh3.

When the center portion of the elevated paper sheet bundle 100 in theconveying direction (length direction) coincides with the bindingposition X in FIGS. 4, 6, and 10, movement of the paper sheet bundle 100is stopped by the stopper 38, and drive of the paper-made staple 60 iswaited for. The binding position X of the paper sheet and foldingposition Y are set to the same position, that is, the binding positionalso serves as the folding position.

As with FIG. 7, FIG. 11 illustrates a state where the paper-made staple60 is driven into the paper sheet bundle 100 by the saddle stitchingstapler 40 to complete the binding processing of the paper sheet bundle100. The position of the paper sheet bundle 100 is set by the movementof the stopper 38 such that the paper-made staple straddles the foldingposition in the sheet conveying direction. In FIG. 11, the leg portions61 and 62 of the left and right paper-made staples 60 are driven,sandwiching the folding position Y therebetween such that a center of aconnection portion (hereinafter, referred to as “staple leg portionconnection portion 60 a”) of the leg portions 61 and 62 substantiallycoincides with the folding position Y. With this configuration, thestaple leg portion connection portion 60 a of the paper-made staple 60is easily folded with the leg portions 61 and 62 inside upon folding ofthe paper sheet bundle. An interval between the paper-made staples 60 inthe sheet width direction is smaller than that illustrated in FIG. V.This is because the saddle stitching stapler 40 is configured such thatupper and lower parts are separated with the sheet conveying pathinterposed therebetween to allow the drive position of the staple 60 tobe set arbitrarily.

[Configuration of Paper-Made Staple]

The following describes the paper-made staple 60 loaded into the saddlestitching stapler 40 of the present invention with reference to FIGS. 12to 14.

FIGS. 12A to 12C and FIG. 13 are explanatory views illustrating thepaper-made staple 60 and a configuration of the rolled staple 70 inwhich a number of paper-made staples 60 are connected in parallel. Morespecifically, FIG. 12A is a detailed plan view of the paper-made staple60. FIG. 12B is a perspective view illustrating a state where thepaper-made staple 60 is formed into a substantially U-shape. FIG. 12C isa cross-sectional view illustrating a state where the paper sheet bundle100 is bound with the paper-made staple 60. FIG. 13 is an explanatoryview illustrating the rolled staple 70 in which a number of paper-madestaples 60 are wound in a roll shape. The paper-made staple 60 androlled staple 70 can have the following configurations. The basicconfigurations thereof are described in detail in Japanese Patent No.4,952,129 quoted above and Japanese Patent No. 4,894,407.

As illustrated in FIG. 12A, a plurality of the paper-made staples 60each having an elongated and substantially straight shape are connectedin parallel. Each paper-made staple 60 has a width of, e.g., about 6 mmto 12 mm in the up-down direction (connection direction of thepaper-made staples 60) of FIG. 12A and a width of, e.g., about 25 mm to50 mm in the left-right direction (longitudinal direction of thepaper-made staple 60) of FIG. 12A. A portion near an end portion of eachpaper-made staple 60 in the longitudinal direction is formed into atrapezoidal shape, and a width thereof become smaller toward its leadingend. Each paper-made staple 60 has, on a rear surface thereof near anend portion in the longitudinal direction, an adhesive portion 63 coatedwith an adhesive.

Further, elliptic feed holes are formed at positions spaced apart by apredetermined distance from both end portions of sides of the adjacenttwo paper-made staples 60. A portion between the two feed holes servesas a slit portion, whereby the paper-made staples 60 are completelyseparated from one another. A portion from an outside end of the feedhole to an end portion of the side connected to the adjacent paper-madestaple 60 serves as a connection portion 68 through which the paper-madestaples 60 are connected. A feed pawl on the saddle stitching stapler 40side is engaged with the two feed holes feed pawl, thereby graduallyfeeding the paper-made staples 60.

The paper-made staple 60 has a folding position slit 64 obtained bycutting inward a substantial center position of the staple leg portionconnection portion 60 a connecting the leg portions in the longitudinaldirection of the staple. The folding position slit 64 is formed for easyand reliable folding of the paper-made staple 60 together with the papersheet bundle 100 in the folding processing to be described later.

The individual paper-made staple 60 is separated from theconnected-state staples illustrated in FIG. 12A by the saddle stitchingstapler 40, and then, as illustrated in FIG. 12B, formed into asubstantially U-shape defined by the staple leg portion connectionportion 60 a and leg portions 61 and 62 bent at left and right ends ofthe staple leg portion connection portion 60 a at substantially rightangles. Then, as illustrated in FIG. 12C, in the paper-made staple 60formed into the substantially U-shape, both the leg portions 61 and 62penetrating the paper sheet bundle 100 are bent along the paper sheetbundle 100, and one leg portion 61 and the other leg portion 62 havingthe adhesive portion 63 are bonded to each other. Then, when the papersheet bundle 100 is folded with the leg portion side inside in a statewhere the paper sheet bundle 100 is bound with the paper-made staple 60,the paper-made staple 60 can easily be folded since the folding positionslit 64 is formed in the substantial center portion of the staple legportion connection portion 60 a connecting the leg portions 61 and 62.

The paper-made staple 60 illustrated in FIGS. 12A to 12C has theadhesive portion 63 on the rear surface of one leg portion 62 in thelongitudinal direction; however, the adhesive portion 63 may be providedon rear surfaces of both leg portions 61 and 62. In this case, not onlythe leg portions 61 and 62 are bonded to each other, but also the legportion 61 is bonded to a rear surface of the paper sheet bundle,thereby increasing the bonding strength. Also in this paper-made staple60, the folding position slit 64 is formed in the staple leg portionconnection portion 60 a, so that the paper-made staple 60 can reliablybe folded. As illustrated in FIG. 13, the paper-made staples 60 arewound in a roll shape (rolled staple 70) and housed in the saddlestitching stapler 40.

Further, the paper-made staple 60 of the present invention is subjectedto the following processing so as to be reliably folded after thebinding processing. That is, the paper-made staple 60 has, in additionto the folding position slit 64 of FIG. 12A formed in the center portionof the staple leg portion connection portion 60 a, the folding positionslits 64 in the both leg portions 61 and 62 as illustrated in FIG. 14A.Thus, as illustrated in FIG. 14B, when the leg portions are bonded toeach other, the folding position slit 64 of the staple leg portionconnection portion 60 a and leg portion side folding position slits 65and 66 overlap with each other. When the folding processing isperformed, the paper-made staple 60 is folded at the folding positionslits 64, 65, and 66.

Particularly, in the configuration illustrated in FIGS. 14A and 14B, awidth β of each of the folding position slits 65 and 66 in the slitlongitudinal direction is set larger than a width α of the foldingposition slit 64 in the stapler longitudinal direction (β>α). Thus, evenwhen the number of the paper sheets to be bundled are increased to causea slight displacement of the leg side folding position slits, thefolding position slit 64 of the staple leg portion connection portion 60a and leg portion side folding position slits 65 and 66 overlap witheach other. As a result, the paper-made staple 60 is folded at theoverlapping range and can thus be folded at the substantially centerportion of the paper-made staple 60 in the longitudinal directiontogether with the paper sheet bundle 100 bound with this paper-madestaple 60.

[Configuration of Folding Roller]

The following describes a configuration of the folding roller 45. Thefolding roller 45 for folding the paper sheet bundle as illustrated inFIG. 15A and folding blade 46 for inserting the paper sheet bundle intoa nip position NP of the folding roller 45 are disposed at the foldingposition Y set on the downstream side of the saddle stitching stapler40. The folding roller 45 includes rollers 45 a and 45 b which arebrought into pressure contact with each other, and each of the rollers45 a and 45 b have a length corresponding to the substantially maximumwidth of the paper sheet. Rotary shafts 45 ax and 45 bx of therespective rollers 45 a and 45 b constituting the folding roller 45 arefitted to long grooves of a not illustrated device frame and are biasedin a pressure-contact direction by respective compression springs 45 aSand 45 bS so as to bring the rollers 45 a and 45 b into pressure contactwith each other. The folding roller 45 may have a structure in which atleast one of the rollers 45 a and 45 b is axially supported so as to bemovable to the pressure-contact direction and is provided with thecompression spring.

The pair of rollers 45 a and 45 b are each formed of a material, such asa rubber, having a large friction coefficient. This is for conveying thepaper sheet bundle in a roller rotation direction while folding the sameby a soft material such as a rubber, and the rollers 45 a and 45 b maybe formed by applying lining to a rubber material.

The folding roller 45 has a concavo-convex shape as illustrated in FIG.17, and predetermined gaps 144 are disposed in the sheet widthdirection. FIG. 17 only illustrates one roller 45 a of the foldingroller 45; actually, however, the other roller 45 b having the sameconfiguration is brought into pressure contact with the roller 45 a asillustrated in FIG. 15A.

The roller 45 a of the folding roller 45 has, from one end to a centerthereof, a large-diameter portion 145 long in the sheet width direction,a folding roller small-diameter portion 146 into which a leading end ofthe folding blade 46 to be described later, a large diameter portion 147short in the sheet width direction, and the long large-diameter portion147. The roller 45 a has a left-right symmetric shape with respect tothe center thereof as illustrated in FIG. 17, and the other roller 45 bnot illustrated in FIG. 17 also has the same shape. Thus, in each of therollers 45 a and 45 b, the above-mentioned gaps 144 are formed in rangescorresponding to the roller small-diameter portions 146. The gaps 144are disposed so as to corresponding to the convexities of the foldingblade 46 as described below. This allows the leading end of the foldingblade to easily enter the nip between the rollers 45 a and 45 b.

Further, as illustrated in FIG. 17, the leading end of the folding bladehas a configuration in which a folding blade short portion 141 (longestleading end portion of the folding blade 46 in a direction perpendicularto a length direction of the folding roller 45) corresponding to the gap144, i.e., the roller small-diameter portion 146 is located closest to ajoining point 45 sg of the folding roller 45, and a folding blade longportion 140 (shortest leading end portion of the folding blade 46 in thedirection perpendicular to a length direction of the folding roller 45corresponding to the roller large-diameter portion 145 is locatedfarthest from the joining point 45 sg of the folding roller 45. Withthis configuration, it is possible to reliably insert the folding bladeshort portion 141 between the folding rollers 45 a and 45 b so as tofold the paper sheet bundle 100 in half and to prevent the folding bladelong portion 140 from stopping its operation by being held between therollers 45 a and 45 b.

Further, as illustrated in FIG. 17, the roller large-diameter portion147 having a comparatively short width is positioned corresponding to aposition at which the paper-made staple 60 is driven, and a foldingblade moderately long portion 142 having a length shorter than thefolding blade long portion 140 and longer than the folding blade shortportion 141 is positioned corresponding to the roller large-diameterportion 147. That is, the leading end portion of the folding blade 46 isconfigured such that a distance between the folding blade long portion140 and joining point 45 sg of the rollers 45 a and 45 b is set to alargest value L1, a distance between the folding blade short portion 141and joining point 45 sg is set to a smallest value L3, and a distancebetween the folding blade moderately long portion 142 and joining point45 sg of the rollers 45 a and 45 b is set to a value L2 between the L1and L3. In other words, the folding blade moderately long portion 142has an intermediate length y obtained by subtracting a length z from alength x between a leading end of the folding blade long portion 140 anda leading end of the folding blade short portion 141. The length z isset to about 0.3 mm to 0.6 mm.

The intermediate length is set so as to correspond to a portion at whichthe paper-made staple 60 straddles the folding position of the papersheet bundle, and the length of the leading end of the folding blade isset such that a position at which the leg portions 61 and 62 overlapeach other is held by the folding roller as illustrated in FIG. 15A andso as not to hinder the operation of the folding blade 46. Thus, asillustrated in FIG. 15B, the leg portions 61 and 62 of the paper-madestaple 60 penetrating the paper sheet bundle 100 and bonded to eachother are held by the roller large-diameter portions 147 of the foldingroller 45, whereby the paper-made staple can also be folded.

[Another Embodiment of Folding Blade and Folding Roller]

In the folding mechanism illustrated in FIG. 17, the distance betweenthe leading end of the folding blade 46 and joining point 45 sg of therollers 45 a and 45 b is set in three stages, and correspondingly, thediameter of each of the rollers 45 a and 45 b is set in two stages(large- and small-diameter portions). Alternatively, however, aconfiguration as illustrated in FIG. 18 may be adopted.

That is, the folding blade 46 has a two-stage configuration includingthe folding blade long portion 140 corresponding to the large-diameterportion 145 of the roller 45 a, the distance from which to the joiningpoint 45 sg of the rollers 45 a and 45 b is large and the folding bladeshort portion 141 corresponding to the small-diameter portion, thedistance from which to the joining point 45 sg is small. The rollers 45a and 45 b each include, in addition to the folding rollerlarge-diameter portion 145 and folding roller small-diameter portion146, a roller intermediate-diameter portion 148 having an intermediatediameter between the diameters of the folding roller large-diameterportion 145 and folding roller small-diameter portion 146 at a positioncorresponding to the folding blade short portion 141. The position ofthe intermediate-diameter portion 148 corresponds to the portion atwhich the paper-made staple 60 straddles the folding position of thepaper sheet bundle 100.

Thus, the folding blade short portion 141 pushes the paper sheet bundleinto the gap 144 between the folding roller small-diameter portions 146.On the other hand, a range corresponding to the binding position of thepaper-made staple 60 corresponds to the intermediate-diameter portion148, the paper-made staple 60 after binding is pushed toward the foldingroller 45 by the intermediate-diameter portion 148.

Particularly, in the configuration according to the present invention,the folding blade 46 pushes the paper-made staple 60 from the bonded legportions 61 and 62 side, thereby increasing the bonding strength.

Further, as illustrated in FIGS. 16 and 19, by adjusting a degree ofoverlapping between the leg portions 61 and 62 of the paper-made staple60 when the leg portions 61 and 62 are pushed between the rollers 45 aand 45 b by the folding blade short portion 141 of the folding blade 46,it is possible to increase a bonding (binding) degree or foldingaccuracy.

That is, as illustrated in FIG. 19A, when the overlapping area betweenthe leg portions 61 and 62 of the paper-made staple 60 is set large(overlapping area is increased by a length a from the folding position),both the leg portions 61 and 62 are pushed by the folding blade 46, sothat it is expected that the bonding strength between the leg portionsis increased. On the other hand, in FIG. 19B, the leg portions 61 and 62do not overlap each other at an abutting position of the folding blade46. In this case, the folding operation is made easier since the legportions 61 and 62 do not overlap each other. Thus, whether to increasethe bonding (binding) strength or folding accuracy can be setarbitrarily by an operator selecting the position of the paper-madestaple 60.

The above rollers 45 a and 45 b are each connected to a not illustratedroller drive means. The roller drive means includes a roller drive motorM6 and a transmission mechanism (transmission means). The transmissionmeans is constituted by a transmission belt transmitting rotation of theroller drive motor M6 while reducing a speed thereof.

The following describes a configuration of a blade drive means fordriving the folding blade 46. The folding blade 46 is supported to a notillustrated device frame through a guide rail so as to be freely movablein a sheet folding direction (see FIG. 15). More specifically, thefolding blade 46 is supported so as to be reciprocatable between astandby position at which it is retracted from the paper sheet supportedin the stacker section 35 and the nip position NP of the folding roller45. Although not illustrated, the blade drive means for reciprocatingthe folding blade 46 includes a blade drive motor M7 and a transmissionbelt for transmitting rotation of the motor M7.

Thus, when the blade drive motor M7 is forwardly and reversely rotated,the folding blade 46 is reciprocated between the standby position andnip position NP along the guide rail. The folding blade 46 isconstituted by a plate-like member having a knife edge extending in thesheet width direction, and the leading end thereof is formed into theconcavo-convex shape as illustrated in FIGS. 17 and 18.

[Folding Operation]

The following describes a state where the paper sheet bundle is foldedby the folding roller 45 and folding blade 46 having the aboveconfigurations with reference to FIGS. 15A to 15D. The paper sheetbundle 100 supported in a bundle in the stacker section 35 is stopped bythe stopper in a state illustrated in FIG. 15A, and the folding positionof the paper sheet bundle 100, at which the stapler has been driven, ispositioned at the folding position Y.

As described above, the paper sheet bundle 100 has been bound with thepaper-made staple 60 by the saddle stitching stapler 40 and, asillustrated, the staple leg portion connection portion 60 a of thepaper-made staple 60 is positioned on the folding roller 45 side, andleg portions 61 and 62 are positioned on the folding blade 46 side. Thestaple leg portion connection portion 60 a straddles the foldingposition Y of the folding blade 46. In FIG. 15A, the staple leg portionconnection portion 60 a is positioned at the substantial center. Thisposition is controlled by the stopper 38 that regulates a leading end ofthe paper sheet bundle and, a set completion signal is output when thepaper sheet bundle 100 is set at this position.

Upon acquisition of the set completion signal, a sheet bundle foldingoperation controller 97 rotates the motor M6 at a speed lower than amoving speed of the folding blade 46. This is for producing a conditionunder which the first and second rollers 45 a and 45 b are driven intorotation by the paper sheet bundle to be inserted into the nip positionby the folding blade 46, as described later.

The sheet bundle folding operation controller 97 moves the folding blade46 from the standby position to nip position NP at a predetermined speedVB. On the other hand, a rotary peripheral speed VR of the foldingroller 45 is set to zero or a value lower than the moving speed VB.Then, as illustrated in FIG. 15B, the paper sheet bundle is bent by thefolding blade 46 at the folding position and is inserted between thefirst and second rollers 45 a and 45 b. At this time, the first andsecond rollers 45 a and 45 b are driven into rotation along with themovement of the paper sheet bundle by the folding blade 46. Then, thesheet bundle folding operation controller 97 stops the blade drive motorM7 after elapse of an estimated time period during which the paper sheetbundle 100 reaches a predetermined nip position to stop the foldingblade 46 at a position illustrated in FIG. 15C. In this state, thepaper-made staple 60 is also folded and held between the rollers 45 aand 45 b. Further, the folding blade 46 is pushed to the leg portions 61and 62 side of the paper-made staple 60, so that the bonding strengthbetween the leg portions is increased. This state is illustrated in FIG.16 as a perspective view.

Thereafter, the sheet bundle folding operation controller 97 drives thefirst and second rollers 45 a and 45 b in rotation once again. Then, thepaper sheet bundle 100 is fed in a delivery direction (leftward in FIG.15D).

Thereafter, as illustrated in FIG. 15D, the sheet bundle foldingoperation controller 97 moves the folding blade 46 positioned at the nipposition NP to the standby position concurrently with the delivery ofthe paper sheet bundle 100 by the rollers 45 a and 45 b.

At the same time, the paper sheet bundle 100 and paper-made staple 60straddling the folding portion of the paper sheet bundle 100 are foldedwith the leg portions 61 and 62 of the paper-made staple 60 inside. As aresult, in a folded state, the leg portions 61 and 62 are positionedinside a booklet, so that peeling of the bonded portion and turning-upof the leg portions 61 and 62.

[Control Configuration]

The following describes a control configuration of the above-describedimage forming system with reference to a block diagram of FIG. 20. Theimage forming system illustrated in FIG. 1 includes a controller(hereinafter, referred to as “main controller”) 80 of the image formingdevice A and a controller (hereinafter, referred to as “post-processingcontroller”) 90 of the sheet post-processing device B. The maincontroller 80 includes an image forming controller 81, a sheet supplycontroller 85, and an input section 83. A user sets “image forming mode”or “post-processing mode” through a controller panel 18 provided in theinput section 83. As described above, in the image forming mode, theimage forming conditions such as a print copy count specification, asheet size specification, a color or black-and-white printingspecification, enlarged or reduced printing specification, a single- ordouble-side printing specification are set. Then, the main controller 80controls the image forming controller and sheet supply controlleraccording to the set image forming conditions to form an image onto apredetermined paper sheet and carries out the resultant paper sheetthrough the main body discharge port 3.

At the same time, the user sets the post-processing mode through thecontroller panel 18. The post-processing mode includes, e.g., a“print-out mode”, a “staple-binding mode”, and a “sheet bundle foldingmode”. The main controller 80 transfers the set post-processing mode,copy number information, and binding mode (binding at one or a pluralityof positions) information to the post-processing controller 90. At thesame time, the main controller 80 transfers a job completion signal tothe post-processing controller 90 every time the image formation iscompleted.

The post-processing controller 90 includes a control CPU 91 thatoperates the sheet post-processing device B in accordance with thespecified mode, a ROM 92 that stores an operation program, and a RAM 93that stores control data. The control CPU 91 includes a sheet conveyingcontroller 94 that executes conveyance of the paper sheet fed to thecarry-in port 23, a sheet stacking operation controller 95 that executessheet stacking operation, a sheet binding operation controller 96 thatexecutes sheet binding processing, and a sheet bundle folding operationcontroller 97 that executes sheet bundle folding operation.

The sheet conveying controller 94 is connected to a control circuit ofthe drive motor M1 for the carry-in roller 24 and sheet discharge roller25 disposed in the sheet carry-in path P1 so as to receive a detectionsignal from a sheet sensor SE1 disposed in the sheet carry-in path P1.The sheet stacking operation controller 95 is connected to drivecircuits of the respective forward/backward rotation motor M2 and sheetdischarge motor M3 for the rear end regulating member 32 so as to stackthe paper sheets in the processing tray 29. The sheet binding operationcontroller 96 is connected to drive circuits of the drive motor 56 andclincher motor 122 incorporated respectively in the end surface stapler33 disposed in the processing tray 29 and saddle stitching stapler 40 ofthe stacker section 35.

The sheet bundle folding operation controller 97 is connected to a drivecircuit of the roller drive motor M6 that drives the rollers 45 a and 45b (first and second folding rollers in FIG. 20) of the folding roller 45into rotation and a drive circuit of the blade drive motor M7 that movesthe folding blade 46 for pushing the paper sheet bundle between therollers 45 a and 45 b of the folding roller 45. Further, the sheetbundle folding operation controller 97 is connected to a control circuitof the shift means MS that controls movement of the stopper 38 of thestacker section 35 to a predetermined position.

The post-processing controller 90 thus configured controls the sheetpost-processing device to execute the following processing operations.

[Print-out Mode]

In this print-out mode, the image forming device A performs imageformation on a series of pages from the first page and sequentiallycarries out in facedown the resultant pages from the main body dischargeport 3. Correspondingly, the sheet post-processing device B moves thepath switching piece 27 to a position indicated by a continuous line ofFIG. 3. As a result, the paper sheet fed to the sheet carry-in path P1is guided to the sheet discharge roller 25. After elapse of an estimatedtime period (estimated based on a signal output by a sheet sensor SE1detecting a leading end of the paper sheet) during which a leading ofthe paper sheet reaches the forward/backward rotation roller 30 of theprocessing tray 29, the sheet conveying controller 94 moves down theforward/backward rotation roller 30 from an upper standby position tothe tray and rotates the same in a clockwise direction in FIG. 3. Then,the paper sheet entering the processing tray 29 is carried out towardthe first sheet discharge tray 21 and housed thereon. In this manner,the subsequent paper sheets are sequentially carried out to the firstsheet discharge tray 21 and housed thereon.

Thus, in the print-out mode, the paper sheet onto which an image hasbeen formed by the image forming device A is housed on the first sheetdischarge tray 21 through the sheet carry-in path P1 of the sheetpost-processing device B. On the first sheet discharge tray 21, thepaper sheets are sequentially stacked upward in facedown in the orderfrom the first page to n-th page.

[Staple Binding Mode]

In this staple binding mode, the image forming device A performs imageformation on a series of pages from the first page to n-th page andsequentially carries out in facedown the resultant pages from the mainbody discharge port 3, as in the print-out mode. Correspondingly, thesheet post-processing device B moves the path switching piece 27 to aposition indicated by the continuous line of FIG. 3. As a result, thepaper sheet fed to the sheet carry-in path P1 is guided to the sheetdischarge roller 25. After elapse of an estimated time period (estimatedbased on the signal output by the sheet sensor SE1 detecting the leadingend of the paper sheet) during which the leading of the paper sheetreaches the forward/backward rotation roller 30 of the processing tray29, the sheet conveying controller 94 moves down the forward/backwardrotation roller 30 from the upper standby position to the tray androtates the same in the clockwise direction in FIG. 3. Then, afterelapse of an estimated time period during which a rear end of the papersheet is carried-in on the tray 29, the sheet conveying controller 94drives the forward/backward rotation roller 30 into rotation in acounterclockwise direction in FIG. 3. Then, the paper sheet fed from thesheet discharge port 25 a is conveyed in a switchback manner along thefirst switchback conveying path SP1 toward the processing tray 29. Byrepeating this sheet conveying operation, a series of the paper sheetsare stacked in facedown on the processing tray 29 in a bundled state.

Every time the paper sheet is stacked on the processing tray 29, thepost-processing controller 90 activates a side aligning plate 34 b toalign width direction positions of the paper sheets to be stacked. Then,upon reception of the job completion signal from the image formingdevice A, the CPU 91 activates the end surface stapler 33 to bind rearend edges of the paper sheet bundle stacked on the tray. After thisstapling operation, the sheet stacking operation controller 95 moves therear end regulating member 32 serving also as a bundle carry-out meansfrom a position indicated by a dashed line of FIG. 3 toward the firstsheet discharge tray 21. Then, the staple-bound paper sheet bundle iscarried out onto the first sheet discharge tray 21 and housed thereon.As a result, a series of the paper sheets onto each of which the imagehas been formed by the image forming device A are staple-bound andhoused on the first sheet discharge tray 21.

[Sheet Bundle Folding Mode]

In this sheet bundle folding mode, the image forming device A finishesthe paper sheet bundle to a booklet shape using the sheetpost-processing device B. To this end, the sheet post-processing deviceB moves the path switching piece 27 of the sheet carry-in path P1 to theposition indicated by the continuous line of FIG. 3. As a result, thepaper sheet fed to the sheet carry-in path P1 is guided to the sheetdischarge roller 25. Then, with reference to a signal from the sheetsensor SE1 detecting the leading end of the paper sheet, the sheetdischarge roller 25 is stopped at a timing at which the rear end of thepaper sheet passes the path switching piece 27 and, at the same time,the path switching piece 27 is moved to a position indicated by a dashedline of FIG. 3. Then, the sheet discharge roller 25 is rotated backward(in the counterclockwise direction in FIG. 3). Then, the conveyingdirection of the paper sheet entering the sheet carry-in path F1 isreversed, with the result that the paper sheet is guided from the pathswitching piece 27 to the second switchback conveying path SP2 and thenguided to the second processing tray (stacker) by the conveying rollers36 and 37 disposed in the second switchback conveying path SP2.

At a timing at which the paper sheet is carried in from the secondswitchback conveying path SP2 to the stacker section 35, the sheetbundle folding operation controller 97 serving as a stopper controllermoves the stopper 38 for regulating the sheet leading end to a position(in this case, position Sh1) corresponding to a sheet length through theshift means control circuit MS. Then, the paper sheet is supported bythe stacker section as a whole. In this state, the post-processingcontroller 90 activates an aligning member 39 to align the paper sheetsin the width direction thereof. The aligning member 39 need not beactivated when the first sheet is housed in the stacker section 35.Further, the aligning member 39 need not be activated every time thepaper sheet is housed in the stacker section 35.

Then, the sheet bundle folding operation controller 97 moves the stopper38 to the position Sh3 at which the sheet rear end enters the switchbackapproaching path 35 a. Then, the rear end of the paper sheet supportedby the guide of the stacker section 35 enters the switchback approachingpath 35 a. In this state, the subsequent paper sheets are fed from thesecond switchback conveying path SP2 to the stacker section 35 andstacked on the preceding paper sheet. Then, in accordance with thecarrying-in of the subsequent paper sheets, the stopper 38 is moved fromthe position Sh3 to the position Sh1 side. Thus, the positions Sh1, Sh2,and Sh3 which are stop positions of the stopper 38 correspondrespectively to the folding position, binding position, and subsequentsheet receiving position.

As above, the aligning member 39 is activated to align the carried-inpaper sheet and paper sheets supported on the guide with each other inthe width direction. By repeating such operations, the paper sheets oneach of which the image has been formed by the image forming device Aare conveyed, through the second switchback conveying path SP2, onto thestacker section 35 and are then aligned. Then, the sheet bundle foldingoperation controller 97 receives the job completion signal and moves thestopper 38 to the position Sh2 to position the center of the paper sheetbundle at the binding position X.

Then, the sheet binding operation controller 96 activates the saddlestitching stapler 40 to staple-bind the paper sheet bundle at twopositions around the sheet center (the number of the binding positionsmay be changed according to the need, and, for example, one or two ormore binding positions may be set). Upon reception of a completionsignal of the binding operation, the sheet bundle folding operationcontroller 97 moves the stopper 38 to the position Sh1 to position thesheet center at the folding position Y. Then, the folding processing isperformed for the paper sheet bundle 100 with a sequence illustrated inFIGS. 15A to 15D, and then the resultant paper sheet bundle 100 iscarried out to the second discharge tray 22.

As described above, the sheet post-processing device according to thepresent invention is configured to bind the paper sheet bundle with thepaper-made staple 60 at the folding position along which the paper sheetbundle is folded such that the staple leg portion connection portion 60a of the paper-made staple 60 connecting the staple leg portions 61 and62 is positioned so as to straddle the sheet folding position in adirection substantially crossing the same, i.e., in the sheet conveyingdirection, and the post-processing controller 90 sets the position ofthe paper sheet bundle by means of the stopper 38 so as to allow thepaper sheet bundle 100 and staple leg portion connection portion 60 a ofthe paper-made staple 60 for use in binding the paper sheet bundle to befolded by the folding roller 45 and folding blade 46.

Thus, the paper sheet bundle can be bound without use of the metallicstaple as in the conventional approach, and the paper sheet bundlefolded in a booklet form can be opened at the folding position with lessdamage of the paper sheets and less feeling of strangeness than in theconventional approach.

1. A sheet post-processing device that binds and holds paper sheets,comprising: a stacker section that temporarily stores the paper sheetsas a paper sheet bundle; a movable stopper that regulates the sheetbundle carried into the stacker section; a binding section that bindsthe paper sheet bundle regulated in position by the stopper; a foldingsection that folds the paper sheet bundle bound by the binding sectionat a predetermined folding position of the paper sheet bundle; and acontroller that controls movement of the stopper, wherein the bindingsection binds the paper sheet bundle at a predetermined binding positionwith a paper-made staple, and the controller controls the movement ofthe stopper such that the paper-made staple is positioned so as tostraddle the predetermined folding position.
 2. The sheetpost-processing device according to claim 1, wherein the folding sectionincludes a folding blade that moves toward the folding position of thepaper sheet bundle in such a direction as to fold the paper sheet bundleand a pair of folding rollers that nip therebetween the paper sheetbundle folded by the folding blade, and the paper-made staple includesleg portions penetrating the paper sheet bundle and then bent inward, aconnection portion connecting the leg portions, and a bonding portionthat bonds the bent leg portions, the connection portion beingpositioned so as to straddle the folding position in a sheet conveyingdirection.
 3. The sheet post-processing device according to claim 2,wherein the folding blade that pushes the paper sheet bundle intobetween the folding rollers so as to fold the paper sheet bundle abutsagainst the leg portions that are bent inward after penetration of thepaper sheet bundle.
 4. The sheet post-processing device according toclaim 3, wherein the folding blade that pushes the paper sheet bundleinto between the folding rollers so as to fold the paper sheet bundleabuts against the adhesive-coated leg portions that are bent inwardafter penetration of the paper sheet bundle.
 5. The sheetpost-processing device according to claim 1, wherein the binding sectionthat drives the paper-made staple into the paper sheet bundle isprovided on a upstream side relative to the folding section in a sheetcarrying-in direction.
 6. The sheet post-processing device according toclaim 2, wherein the controller sets a moving amount of the stopper suchthat the connection portion of the paper-made staple is positioned so asto straddle the folding position in the sheet carrying-in direction. 7.A sheet post-processing device comprising: a stacker section thattemporarily stores, in a substantially vertical attitude, the papersheets as a paper sheet bundle; a movable stopper that regulates thesheet bundle carried into the stacker section; a binding section thatbinds the paper sheet bundle regulated in position by the stopper; afolding section that folds the paper sheet bundle bound by the bindingsection at a predetermined folding position of the paper sheet bundle;and a controller that controls movement of the stopper, wherein thebinding section binds the paper sheet bundle with a paper-made staple,the paper-made staple including leg portions penetrating the paper sheetbundle and then bent inward, a connection portion connecting the legportions, and a bonding portion that bonds the bent leg portions, thefolding section includes a folding blade that moves toward the foldingposition of the paper sheet bundle which substantially corresponds to acenter of the paper sheet bundle in a sheet conveying direction, in sucha direction as to fold the paper sheet bundle and a pair of foldingrollers that nip therebetween the paper sheet bundle folded by thefolding blade, and the controller controls the stopper portion such thata position of the paper sheet bundle is set such that sheet penetrationpositions of the leg portions of the paper-made staple sandwichtherebetween the folding position.
 8. The sheet post-processing deviceaccording to claim 2, wherein the folding blade and each of the pair offolding rollers have concavo-convex shapes corresponding to each other,and a length of the folding blade or a diameter of the folding rollercorresponding to the binding position is set to an intermediate lengthor diameter between sizes of the concavity and convexity.
 9. The sheetpost-processing device according to claim 8, wherein the pair of foldingrollers each include a large-diameter portion and a small-diameterportion, the folding blade includes a short-length portion and along-length portion in terms of a distance from a joining positionbetween the folding rollers, and a length of the folding bladecorresponding to the binding position is set to an intermediate lengthbetween lengths of the short-length and long-length portions.
 10. Thesheet post-processing device according to claim 8, wherein the pair offolding rollers each include a large-diameter portion and asmall-diameter portion, the folding roller has, corresponding to thelarge-diameter portion, an area the distance from which to a joiningposition between the folding rollers is large and has, corresponding tothe small-diameter portion, an area the distance from which to thejoining position between the folding rollers is small, and correspondingto the binding position, the large diameter portion of each of thefolding rollers and an area of the folding blade having an intermediatelength between lengths of the area thereof the distance from which tothe joining position is large and area thereof the distance from whichto the joining position is small are positioned.
 11. The sheetpost-processing device according to claim 8, wherein the folding bladehas areas the distances from which to a joining position between thefolding rollers are small and large, the folding rollers each have alarge-diameter portion, a small-diameter portion, and anintermediate-diameter portion, the large-diameter portion correspondingto a large distance from the joining position between the foldingrollers, the small-diameter position corresponding to a small distancefrom the joining position between the folding rollers, and correspondingto the binding position, the area of the folding blade the distancesfrom which to the joining position between the folding rollers is smalland the intermediate-diameter portion of each of the folding rollers arepositioned.
 12. The sheet post-processing device according to claim 2,wherein the paper-made staple further has a cut at an end portion of theconnection portion in a direction crossing a longitudinal directionthereof so as to correspond to the folding position for the purpose offacilitating the folding of the connection portion.
 13. The sheetpost-processing device according to claim 12, wherein the cut is formedinward from the edge portion so as to have a substantially triangularshape and is provided on both edge portions of the connection portion.14. A paper-made staple for use in a sheet post-processing device thatperforms sheet binding and folding processing, the paper-made staplebeing configured to bind a paper sheet bundle, straddling apredetermined folding position of the paper sheet bundle and to befolded by folding rollers and a folding blade constituting a foldingsection of the sheet post-processing device together with the papersheet bundle, the paper-made staple comprising: a pair of leg portionsinserted into the paper sheet bundle and then bent inward; and a stapleconnection portion that connects the leg portions in a staplelongitudinal direction, wherein the connection portion has a cut in adirection crossing a longitudinal direction thereof at a positioncorresponding to the folding position for the purpose of facilitatingthe folding thereof, and each of the leg portions has a leg portion sidecut at a position overlapping the cut of the connection portion when theleg portions are bent inward.
 15. An image forming device comprising: animage forming unit that sequentially forms an image onto paper sheets;and a sheet post-processing device that performs post-processing for thepaper sheet fed from the image forming unit, the sheet post-processingdevice having the configurations as claimed in claim 1.